"That was the greatest comic tour de force that anybody had seen in a long time."
(Roger Rabbit)
The line integral was introduced after the catenary problem,
basically at the end of otherwise a chapter in the text, instead
of starting a new chaper, the "advanced calculus". So, I wanted
to make the line integral the same as the quarter-bend, but instead
it was both amounting to the catenary via parabola, and, that
I want to solve the catenary in the parabola, but, otherwise the
line integral was let down to line elements and ds.
Then the surface integral, after surfaces of revolution, or paint cans,
then the path of integration is free for what it is, what it amounts to.
So, I'd imagine several line integral setups for usual problems of
what is the length according to perimeter, circumference, besides
as wise the square, and quadratic, in the elements, and the paths.
This is where according to the paths there are elements that are
integrable, that any contrivance in symmetry or exhaust, or relation
in measure here length, is for usual geometric and stateful examples,
in terms of how and why they are line elements and path elements.
The "advanced calculus", ..., here when it got to "yes I have derived this
Green's function accordingly, but, what I want is instead for example
different elements", then though later after gradient descent and
Stokes, then again out through the Hamiltonian what really though
is for the Hermitian, then to flow and what is fluid mechanics and
fluid dynamics, then again it was "still these are Green's functions
after Stokes, 'advanced calculus'", I've studied the advanced calculus,
and have several texts, but surely most my exposure is peripheral.
I.e. the brief tableau for the determinantal, the "dot product is ...
derivative anti-integral placeholder-element", is for people to
learn inner and outer products and wedge and dot and so on.
And why and how it's computable.
Read this "Exterior derivative" Wiki:
https://en.wikipedia.org/wiki/Exterior_derivative
Then you'll notice it's as if I intend to paste the above into it.